Buying an iMac w/o Fusion

As it works out, I've got credit with two dealers. But neither offers the 27" iMac with FD.

My needs: photo. Photo, More photo.

I'm retired and so my present G4 tower is only for word processing and Internet access.

Soooo...... were I to get an iMac without Fusion, and instead get a 1TB drive internal and then buy a 3rd party SDD external for booting the OS and storing applications (USB 3 or TB cable), what exactly am I missing out on? Be specific.